Path類詳解

原文連接：https://blog.csdn.net/qq877728715/article/details/104499687/

文章目錄

• Java7新增文件IO類
• 一.Paths
• • 1.建立Paths
• 二.Path
• • 1.建立Path
  • • 1.1.建立Path的三種方式
  • 2.Path經常使用方法
• 三.Files
• • 1.判斷方法：
  • 2.刪除方法
  • 3.複製方法
  • 4.移動和重命名方法
  • 5.建立文件和文件夾方法
  • 6.文件屬性方法
  • 7.讀取、編輯文件內容方法
  • 8.遍歷文件列表方法
• 四.Path和Files使用
• 五.FileTime對象

Java7新增文件IO類

Java7中文件IO發生了很大的變化，專門引入了不少新的類：

java.nio.file.DirectoryStream;
java.nio.file.FileSystem;
java.nio.file.FileSystems;
java.nio.file.Files;
java.nio.file.Path;
java.nio.file.Paths;
java.nio.file.attribute.FileAttribute;
java.nio.file.attribute.PosixFilePermission;
java.nio.file.attribute.PosixFilePermissions;

在java中文件或是目錄習慣用java.io.File對象來表示，可是File類有不少缺陷

• 它的不少方法不能拋出異常

• 它的delete方法常常莫名其妙的失敗等，舊的File類常常是程序失敗的根源。

• 所以在Java7中有了更好的替代：java.nio.file.Path及java.nio.file.Files。

  • Path接口的名字很是恰當，就是表示路徑的，API中講Path對象能夠是一個文件，一個目錄，或是一個符號連接，也能夠是一個根目錄。 用法很簡單。建立Path並不會建立物理文件或是目錄，path實例常常引用並不存在的物理對象，要真正建立文件或是目錄，須要用到Files類。

  • Files類是一個很是強大的類，它提供了處理文件和目錄以及讀取文件和寫入文件的靜態方法。 能夠用它建立和刪除路徑。複製文件。檢查路徑是否存在等。 此外。Files還擁有建立流對象的方法。

一.Paths

Paths類僅由靜態方法組成，經過轉換路徑字符串返回Path或URI。

• 由於就兩個方法用來生成Path對象，以供Path和Files使用；而Path也常常由Paths來生成，又或者File類有一個toPath();方法能夠使用

1.建立Paths

 
 
 
 
 
 
  
  
           
  
  

 
 
 
 
 
 
  
  
           
  
  
static Path get(String first, String... more) 
//將路徑字符串或鏈接到路徑字符串的字符串序列轉換爲 Path，能夠get("c:/abc");或者get("c:","abc")，注意這裏能夠有多個參數String... more表明n個參數，這個比較經常使用
static Path get(URI uri) 
//將給定的URI轉換爲Path對象

二.Path

Path就是取代File的，用於來表示文件路徑和文件。能夠有多種方法來構造一個Path對象來表示一個文件路徑，或者一個文件：
- 該接口的實現是不可變且安全的，可供多個並行線程使用。

1.建立Path

 
 
 
 
 
 
  
  
           
  
  

 
 
 
 
 
 
  
  
           
  
  
Path toPath() 
//File類對象方法--返回一個java.nio.file.Path對象
abstract Path getPath(String first, String... more) 
//FileSystem對象方法--將路徑字符串或從路徑字符串鏈接起來的一系列字符串轉換爲 Path 。 

1.1.建立Path的三種方式

建立Path的三種方式

Path path=FileSystems.getDefault().getPath("d:/users/日記5.txt");    
//並無實際建立路徑，而是一個指向d:/users/日記5.txt路徑的引用

Path path=Paths.get(「d:/users/日記5.txt」); //Paths類提供了這個快捷方法，直接經過它的靜態get方法建立path

Path path= = new File(「d:/users/日記5.txt」).toPath();

2.Path經常使用方法

Path接口沒什麼判斷方法，其實更多的判斷和操做都在Files工具類裏面

boolean isAbsolute() 
//告訴這條路是不是絕對的
boolean endsWith(Path other) 
//測試此路徑是否以給定的路徑結束
boolean endsWith(String other) 
//測試此路徑是否以給定字符串結束，如"c:/a/banana/cat"能夠以"/banana/cat"結尾，但不能以"t"結尾
boolean startsWith(Path other) 
//測試此路徑是否以給定的路徑開始。 
boolean startsWith(String other) 
//測試此路徑是否以給定字符串開始，跟上面同樣規律

Path getFileName()
//將此路徑表示的文件或目錄的名稱返回爲 Path對象，文件名或文件夾名，不含路徑
Path getName(int index)
//返回此路徑的名稱元素做爲 Path對象。目錄中最靠近root的爲0，最遠的爲(count-1)，count由下面的方法得到
int getNameCount()
//返回路徑中的名稱元素的數量。0則只有root
Path getParent()
//返回 父路徑，若是此路徑沒有父返回null，如/a/b/c返回/a/b，配合下面的方法消除".「或」…"
Path normalize()
//返回一個路徑，該路徑是冗餘名稱元素的消除。如消除掉"."、"…"
Path getRoot()
//返回此路徑的根組分做爲 Path對象，或 null若是該路徑不具備根組件。如返回"c:/"
Path relativize(Path other)
//構造此路徑和給定路徑之間的相對路徑。有點難理解，p1-「Topic.txt」,p2-「Demo.txt」,p3-"/Java/JavaFX/Topic.txt",p4-"/Java/2011"；；那麼p1和p2的結果是"…/Demo.txt"；；p2和p1的結果是"…/Topic.txt"；；p3和p4的結果是"…/…/2011"；；p4和p3的結果是"…/JavaFX/Topic.txt"
Path resolve(String other)
//將給定的路徑字符串轉換爲 Path。如"c:/a/b"和字符串"c.txt"的結果是"c:/a/b/c.txt"；更像是拼接
Path resolveSibling(String other)
//將給定的路徑字符串轉換爲 Path。如"c:/a/b.txt"和字符串"c.txt"的結果是"c:/a/c.txt"；更像是替換
Path subpath(int beginIndex, int endIndex)
//返回一個相對的 Path ，它是該路徑的名稱元素的子序列，如"d:/a/b/c.txt"參數爲(1,3)返回一個"b/c.txt"
Path toAbsolutePath()
//返回表示此路徑的絕對路徑的 Path對象。包括盤符和文件名或文件夾名

Iterator<Path> iterator()
//返回此路徑的名稱元素的迭代器。「c:/a/b/c.txt"的迭代器能夠next出如下"a」「b」「c.txt」
File toFile()
//返回表示此路徑的File對象

三.Files

Files類只包含對文件，目錄或其餘類型文件進行操做的靜態方法。主要和Path接口的對象進行配合使用

1.判斷方法：

 
 
 
 
 
 
  
  
           
  
  

 
 
 
 
 
 
  
  
           
  
  
static boolean exists(Path path, LinkOption... options) 
//測試文件是否存在。 
static boolean notExists(Path path, LinkOption... options) 
//測試此路徑所在的文件是否不存在。 
static boolean isDirectory(Path path, LinkOption... options) 
//測試文件是不是目錄。 
static boolean isExecutable(Path path) 
//測試文件是否可執行。 
static boolean isHidden(Path path) 
//告知文件是否被 隱藏 。 
static boolean isReadable(Path path) 
//測試文件是否可讀。 
static boolean isRegularFile(Path path, LinkOption... options) 
//測試文件是不是具備不透明內容的常規文件。說實話，我也不太懂常規文件指的是啥
static boolean isSameFile(Path path, Path path2) 
//測試兩個路徑是否找到相同的文件。
static boolean isSymbolicLink(Path path) 
//測試文件是不是符號連接。//
static boolean isWritable(Path path) 
//測試文件是否可寫。 

2.刪除方法

 
 
 
 
 
 
  
  
           
  
  

 
 
 
 
 
 
  
  
           
  
  

  
  
  
  
  
   
   
            
   
   
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static boolean deleteIfExists(Path path) 
//刪除文件（若是存在）。 
static void delete(Path path) 
//刪除文件。 

3.複製方法

 
 
 
 
 
 
  
  
           
  
  

 
 
 
 
 
 
  
  
           
  
  
static long copy(InputStream in, Path target, CopyOption... options) 
//將輸入流中的全部字節複製到文件。
//關於CopyOption則是一個被繼承的接口主要有枚舉類StandardCopyOption和LinkOption
// 1.StandardCopyOption
// REPLACE_EXISTING(也就是替換覆蓋)
// COPY_ATTRIBUTES(將源文件的文件屬性信息複製到目標文件中)
// ATOMIC_MOVE(原子性的複製)都是字面意思
// 2.LinkOption
// NOFOLLOW_LINKS
static long copy(Path source, OutputStream out) 
//將文件中的全部字節複製到輸出流。 
static Path copy(Path source, Path target, CopyOption... options) 
//將文件複製到目標文件。 

4.移動和重命名方法

 
 
 
 
 
 
  
  
           
  
  

 
 
 
 
 
 
  
  
           
  
  
static Path move(Path source, Path target, CopyOption... options) 
//將文件移動或重命名爲目標文件。 

5.建立文件和文件夾方法

 
 
 
 
 
 
  
  
           
  
  

 
 
 
 
 
 
  
  
           
  
  
static Path createDirectories(Path dir, FileAttribute<?>... attrs) 
//首先建立全部不存在的父目錄來建立目錄。
static Path createDirectory(Path dir, FileAttribute<?>... attrs) 
//建立一個新的目錄。 
static Path createFile(Path path, FileAttribute<?>... attrs) 
//建立一個新的和空的文件，若是該文件已存在失敗。

6.文件屬性方法

static <V extends FileAttributeView> V getFileAttributeView(Path path, 類<V> type, LinkOption... options) 
//返回給定類型的文件屬性視圖。指定六個視圖其中一種，上面一開始有點到。拿到的xxxAttributeView會有一個跟下面同樣名字的readAttributes方法來獲得一個xxxAttributes真正的獲取操做就全是在這個xxxAttributes類的對象裏get啦
static <A extends BasicFileAttributes> A readAttributes(Path path, 類<A> type, LinkOption... options) 
//讀取文件的屬性做爲批量操做。指定一個xxxAttributes，獲得一個實例，經過裏面的方法獲得時間等基本屬性

static Object getAttribute(Path path, String attribute, LinkOption... options)
//讀取文件屬性的值。這個 String attributes 參數的語法固定是以 view-name:comma-separated-attributes 的形式；view-name指定視圖名如basic,posix,acl等，不寫默認爲basic；有寫默認要加":"；能夠用"basic：「或」"讀取全部，又或者用"basic：size，lastModifiedTime"讀取大小和修改時間。具體還有那些屬性能夠看具體指定的類，好比basic視圖就看BasicFileAttributes這個接口都有哪些方法，能夠讀取哪些文件屬性。同理，下面的 String attributes 同樣是這個理
static Map<String,Object> readAttributes(Path path, String attributes, LinkOption... options)
//讀取一組文件屬性做爲批量操做。
static Path setAttribute(Path path, String attribute, Object value, LinkOption... options)
//設置文件屬性的值。

/* 下面這些也是獲取屬性的方法，不過還沒研究到是怎麼用的 */
static FileTime getLastModifiedTime(Path path, LinkOption... options)
//返回文件的上次修改時間。
static UserPrincipal getOwner(Path path, LinkOption... options)
//返回文件的全部者。
static Set<PosixFilePermission> getPosixFilePermissions(Path path, LinkOption... options)
//返回文件的POSIX文件權限。
static Path setLastModifiedTime(Path path, FileTime time)
//更新文件上次修改的時間屬性。
static Path setOwner(Path path, UserPrincipal owner)
//更新文件全部者。
static Path setPosixFilePermissions(Path path, Set<PosixFilePermission> perms)
//設置文件的POSIX權限。
static long size(Path path)
//返回文件的大小（以字節爲單位）。

7.讀取、編輯文件內容方法

 
 
 
 
 
 
  
  
           
  
  

 
 
 
 
 
 
  
  
           
  
  
static BufferedReader newBufferedReader(Path path) 
//打開一個文件進行閱讀，返回一個 BufferedReader以高效的方式從文件讀取文本。 
static BufferedReader newBufferedReader(Path path, Charset cs) 
//打開一個文件進行閱讀，返回一個 BufferedReader ，能夠用來以有效的方式從文件讀取文本。 
static BufferedWriter newBufferedWriter(Path path, Charset cs, OpenOption... options) 
//打開或建立一個寫入文件，返回一個 BufferedWriter ，能夠用來以有效的方式將文本寫入文件。 
static BufferedWriter newBufferedWriter(Path path, OpenOption... options) 
//打開或建立一個寫入文件，返回一個 BufferedWriter以高效的方式寫入文件。 
static SeekableByteChannel newByteChannel(Path path, OpenOption... options) 
//打開或建立文件，返回可訪問的字節通道以訪問該文件。 
static SeekableByteChannel newByteChannel(Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs) 
//打開或建立文件，返回可訪問的字節通道以訪問該文件。 
static InputStream newInputStream(Path path, OpenOption... options) 
//打開一個文件，返回輸入流以從文件中讀取。 
static OutputStream newOutputStream(Path path, OpenOption... options) 
//打開或建立文件，返回可用於向文件寫入字節的輸出流。 
static byte[] readAllBytes(Path path) 
//讀取文件中的全部字節。 
static List<String> readAllLines(Path path) 
//從文件中讀取全部行。 
static List<String> readAllLines(Path path, Charset cs) 
//從文件中讀取全部行。
static Path write(Path path, byte[] bytes, OpenOption... options) 
//將字節寫入文件。 
static Path write(Path path, Iterable<? extends CharSequence> lines, Charset cs, OpenOption... options) 
//將文本行寫入文件。 
static Path write(Path path, Iterable<? extends CharSequence> lines, OpenOption... options) 
//將文本行寫入文件。 

以上方法適用於處理中等長度的文本文件，若是要處理的文件長度比較大，或者是二進制文件，那麼仍是應該使用流

8.遍歷文件列表方法

• newDirectoryStream只是遍歷當前Path的子目錄列表，或者寫一個方法裏面遞歸調用實現遍歷到底；
• walk則是能夠經過maxDepth參數來決定遍歷的深度，後面的FileVisitOption參數無關緊要；
• list相似於newDirectoryStream，區別是walk和newDirectoryStream是遞歸的，list是非遞歸的

static DirectoryStream<Path> newDirectoryStream(Path dir) 
//打開一個目錄，返回一個DirectoryStream以遍歷目錄中的全部條目。最好用 try-with-resources 構造，能夠自動關閉資源。返回的 DirectoryStream<Path> 其實能夠直接使用 Iterator或者for循環 遍歷每個 dir 下面的文件或目錄
static DirectoryStream<Path> newDirectoryStream(Path dir, DirectoryStream.Filter<? super Path> filter) 
//上面方法的重載，經過實現參數二(有一個 boolean accept(Path p) 方法來判斷文件是否符合須要)來達到過濾的目的。如accept方法中寫"return (Files.size(p) > 8192L);"來匹配大於8k的文件
static DirectoryStream<Path> newDirectoryStream(Path dir, String glob) 
//上面方法的重載，能夠經過參數二做爲過濾匹配出對應的文件。如 newDirectoryStream(dir, "*.java") 用於遍歷目錄裏全部java後綴的文件

static Stream<Path> walk(Path start, FileVisitOption... options)
//深度優先遍歷。返回一個 Stream ，它經過 Path根據給定的起始文件的文件樹懶惰地填充 Path 。
static Stream<Path> walk(Path start, int maxDepth, FileVisitOption... options)
//深度優先遍歷。返回一個 Stream ，它是經過走根據給定的起始文件的文件樹懶惰地填充 Path 。

static Stream<Path> list(Path dir)
//返回一個懶惰的填充 Stream ，其元素是 Stream中的條目。返回的 Stream 裏封裝了一個 DirectoryStream 用於遍歷。

四.Path和Files使用

import org.junit.Test;
import java.io.*;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.StandardCharsets;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.PosixFilePermission;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Stream;

public class PathAndFilesTest {
/**
* 建立Path
*/


@Test
public void createPath() throws URISyntaxException, MalformedURLException {
//1.Paths
Path path = Paths.get(「F:/測試數據.csv」);
System.out.println(path.getFileName());
Path path1 = Paths.get(new URI(「file:///f:/測試數據.csv」));

<span class="token comment">//2.FileSystems</span>
    Path path2 <span class="token operator">=</span> FileSystems<span class="token punctuation">.</span><span class="token function">getDefault</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getPath</span><span class="token punctuation">(</span><span class="token string">"F:/測試數據.csv"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token comment">//3.File</span>
    Path path3 <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">File</span><span class="token punctuation">(</span><span class="token string">"F:/測試數據.csv"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">toPath</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>


<span class="token comment">/**
 * 建立一個空文件/文件夾
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">create</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
    <span class="token comment">//文件夾</span>
    Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/hello"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>Files<span class="token punctuation">.</span><span class="token function">exists</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span><span class="token comment">//若是不存在</span>
        Files<span class="token punctuation">.</span><span class="token function">createDirectory</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token comment">//建立多個目錄</span>
        <span class="token comment">//Files.createDirectories(path);</span>
    <span class="token punctuation">}</span>

    <span class="token comment">//文件</span>
    Path path1 <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/helloFile.txt"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>Files<span class="token punctuation">.</span><span class="token function">exists</span><span class="token punctuation">(</span>path1<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span><span class="token comment">//若是不存在</span>
        Files<span class="token punctuation">.</span><span class="token function">createFile</span><span class="token punctuation">(</span>path1<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 文件屬性
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">getFileProperties</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
    Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/測試數據.csv"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>Files<span class="token punctuation">.</span><span class="token function">getLastModifiedTime</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//最後修改時間:2019-05-22T02:52:45.625094Z</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>Files<span class="token punctuation">.</span><span class="token function">getOwner</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//擁有者:DESKTOP-GE36VVD\87772 (User)</span>
    <span class="token comment">//System.out.println(Files.getPosixFilePermissions(path));//權限,非admin可能會報錯</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>Files<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//文件大小: 34207517</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 讀取一個文本文件
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">readText</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
    Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/test.txt"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment">//經過bufferedReader讀取</span>
    BufferedReader bufferedReader <span class="token operator">=</span> Files<span class="token punctuation">.</span><span class="token function">newBufferedReader</span><span class="token punctuation">(</span>path<span class="token punctuation">,</span> StandardCharsets<span class="token punctuation">.</span>UTF_8<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">///該文件編碼是什麼newBufferedReader就必須指定什麼字符集,不然報錯</span>

    StringBuilder sb <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">StringBuilder</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    String tempString <span class="token operator">=</span> null<span class="token punctuation">;</span>
    <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>tempString <span class="token operator">=</span> bufferedReader<span class="token punctuation">.</span><span class="token function">readLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> null<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
        sb <span class="token operator">=</span> sb<span class="token punctuation">.</span><span class="token function">append</span><span class="token punctuation">(</span>tempString <span class="token operator">+</span> <span class="token string">"\n"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>sb<span class="token punctuation">)</span><span class="token punctuation">;</span>


    <span class="token comment">//經過Files方法readAllLines</span>
    List<span class="token generics function"><span class="token punctuation">&lt;</span>String<span class="token punctuation">&gt;</span></span> strings <span class="token operator">=</span> Files<span class="token punctuation">.</span><span class="token function">readAllLines</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">;</span>
    strings<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span>System<span class="token punctuation">.</span>out<span class="token operator">:</span><span class="token operator">:</span>println<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 拿到文件輸入流
 *
 * @throws IOException
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">getInputStream</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
    Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/test.txt"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    InputStream inputStream <span class="token operator">=</span> Files<span class="token punctuation">.</span><span class="token function">newInputStream</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token comment">//轉換字符流後在包裝成緩衝流</span>
    BufferedReader bufferedReader <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">BufferedReader</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">InputStreamReader</span><span class="token punctuation">(</span>inputStream<span class="token punctuation">,</span> <span class="token string">"UTF-8"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

    StringBuilder sb <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">StringBuilder</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    String tempString <span class="token operator">=</span> null<span class="token punctuation">;</span>
    <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>tempString <span class="token operator">=</span> bufferedReader<span class="token punctuation">.</span><span class="token function">readLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> null<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
        sb <span class="token operator">=</span> sb<span class="token punctuation">.</span><span class="token function">append</span><span class="token punctuation">(</span>tempString <span class="token operator">+</span> <span class="token string">"\n"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>sb<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 文件寫操做
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">writeFile</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
    Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/writeFile.txt"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token comment">//獲取寫入流</span>
    BufferedWriter bufferedWriter <span class="token operator">=</span> Files<span class="token punctuation">.</span><span class="token function">newBufferedWriter</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token comment">//執行寫入操做</span>
    String str <span class="token operator">=</span> <span class="token string">"write file test"</span><span class="token punctuation">;</span>
    bufferedWriter<span class="token punctuation">.</span><span class="token function">write</span><span class="token punctuation">(</span>str<span class="token punctuation">)</span><span class="token punctuation">;</span>

    <span class="token comment">//關閉資源</span>
    bufferedWriter<span class="token punctuation">.</span><span class="token function">flush</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    bufferedWriter<span class="token punctuation">.</span><span class="token function">close</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 遍歷一個文件夾
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">traverseDirectory</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
    Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/test"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    Stream<span class="token generics function"><span class="token punctuation">&lt;</span>Path<span class="token punctuation">&gt;</span></span> list <span class="token operator">=</span> Files<span class="token punctuation">.</span><span class="token function">list</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">;</span>
    list<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span>p <span class="token operator">-</span><span class="token operator">&gt;</span> <span class="token punctuation">{<!-- --></span>
        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>p<span class="token punctuation">.</span><span class="token function">getFileName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 遍歷文件樹
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">traverseTree</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
    Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/test/"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    Stream<span class="token generics function"><span class="token punctuation">&lt;</span>Path<span class="token punctuation">&gt;</span></span> walk <span class="token operator">=</span> Files<span class="token punctuation">.</span><span class="token function">walk</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">;</span>
    walk<span class="token punctuation">.</span><span class="token function">forEach</span><span class="token punctuation">(</span>path1 <span class="token operator">-</span><span class="token operator">&gt;</span> <span class="token punctuation">{<!-- --></span>

// System.out.println(path1.getRoot());//根目錄
System.out.println(path1.getFileName());//文件名
// System.out.println(path1.getParent());//上級目錄
// System.out.println(path1.getFileSystem());//文件系統
});
//還有種方式Files.walkFileTree()
}

<span class="token comment">/**
 * 文件複製
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">copyFile</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
    Path src <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/測試數據.csv"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    Path dest <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/test/Copy測試數據.csv"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    Files<span class="token punctuation">.</span><span class="token function">copy</span><span class="token punctuation">(</span>src<span class="token punctuation">,</span> dest<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token comment">/**
 * 讀取權限見上面示例，設置權限
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">writePermission</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
    Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"F:/test/導出測試數據.xlsx"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    Set<span class="token generics function"><span class="token punctuation">&lt;</span>PosixFilePermission<span class="token punctuation">&gt;</span></span> permissionSet <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">HashSet</span><span class="token operator">&lt;</span><span class="token operator">&gt;</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    permissionSet<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>PosixFilePermission<span class="token punctuation">.</span>GROUP_WRITE<span class="token punctuation">)</span><span class="token punctuation">;</span>
    permissionSet<span class="token punctuation">.</span><span class="token function">add</span><span class="token punctuation">(</span>PosixFilePermission<span class="token punctuation">.</span>OWNER_EXECUTE<span class="token punctuation">)</span><span class="token punctuation">;</span>
    Files<span class="token punctuation">.</span><span class="token function">setPosixFilePermissions</span><span class="token punctuation">(</span>path<span class="token punctuation">,</span> permissionSet<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

/**
* 判斷方法
* @throws IOException
*/



@Test
public void judge() throws IOException {
Path path1 = Paths.get(「f:\test」, 「Copy測試數據.csv」);
Path path2 = Paths.get(「f:\測試數據.csv」);
// boolean exists(Path path, LinkOption … opts) : 判斷文件是否存在
System.out.println(Files.exists(path2, LinkOption.NOFOLLOW_LINKS));//true

// boolean isDirectory(Path path, LinkOption … opts) : 判斷是不是目錄
//不要求此path對應的物理文件存在。
System.out.println(Files.isDirectory(path1, LinkOption.NOFOLLOW_LINKS));//false

// boolean isRegularFile(Path path, LinkOption … opts) : 判斷是不是文件

// boolean isHidden(Path path) : 判斷是不是隱藏文件
//要求此path對應的物理上的文件須要存在。纔可判斷是否隱藏。不然，拋異常。
// System.out.println(Files.isHidden(path1));

// boolean isReadable(Path path) : 判斷文件是否可讀
System.out.println(Files.isReadable(path1));//true
// boolean isWritable(Path path) : 判斷文件是否可寫
System.out.println(Files.isWritable(path1));//true
// boolean notExists(Path path, LinkOption … opts) : 判斷文件是否不存在
System.out.println(Files.notExists(path1, LinkOption.NOFOLLOW_LINKS));//false
}
}

<span class="token comment">/**
 * StandardOpenOption.READ:表示對應的Channel是可讀的。
 * StandardOpenOption.WRITE：表示對應的Channel是可寫的。
 * StandardOpenOption.CREATE：若是要寫出的文件不存在，則建立。若是存在，忽略
 * StandardOpenOption.CREATE_NEW：若是要寫出的文件不存在，則建立。若是存在，拋異常
 */</span>
<span class="token annotation punctuation">@Test</span>
<span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">ioStream</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> IOException <span class="token punctuation">{<!-- --></span>
	Path path1 <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"f:\\test"</span><span class="token punctuation">,</span> <span class="token string">"copyTest.txt"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

// InputStream newInputStream(Path path, OpenOption…how):獲取 InputStream 對象
InputStream inputStream = Files.newInputStream(path1, StandardOpenOption.READ);

// OutputStream newOutputStream(Path path, OpenOption…how) : 獲取 OutputStream 對象
OutputStream outputStream = Files.newOutputStream(path1, StandardOpenOption.WRITE, StandardOpenOption.CREATE);

// SeekableByteChannel newByteChannel(Path path, OpenOption…how) : 獲取與指定文件的鏈接，how 指定打開方式。
SeekableByteChannel channel = Files.newByteChannel(path1, StandardOpenOption.READ, StandardOpenOption.WRITE, StandardOpenOption.CREATE);

// DirectoryStream<Path> newDirectoryStream(Path path) : 打開 path 指定的目錄
Path path2 = Paths.get(「f:\test」);
DirectoryStream<Path> directoryStream = Files.newDirectoryStream(path2);
Iterator<Path> iterator = directoryStream.iterator();
while (iterator.hasNext()) {
System.out.println(iterator.next());
}
}

五.FileTime對象

表示文件時間戳屬性的值，可能會在設置文件最後更新屬性時使用到：

 
 
 
 
 
 
  
  
           
  
  

 
 
 
 
 
 
  
  
           
  
  
static FileTime fromMillis(long value) 
//返回一個 FileTime以 FileTime單位表示給定值。 
long toMillis() 
//返回以毫秒爲單位的值。
String toString() 
//返回此 FileTime的字符串表示 FileTime 。 

栗子：

/** * 可能你要從文件屬性中的FileTime或者到一個Date對象 */
Path pathObj = Paths.get("C:/a/b/c.txt");
BasicFileAttributes attrs = Files.readAttributes(pathObj, BasicFileAttributes.class);
Data date = new Date(attrs.lastModifiedTime().toMillis());

/**

• 又或者可能你要人爲地修改這個文件時間屬性，須要一個FileTime
  */
  Path path = Paths.get(「C:/a/b/c.txt」);
  long time = System.currentTimeMillis();
  FileTime fileTime = FileTime.fromMillis(time);
  try{
  Files.setAttribute(path, 「basic:lastModifiedTime」, fileTime,LinkOption.NOFOLLOW_LINKS);
  }catch (IOException e) {
  System.err.println(e);
  }